The operating machines, such as excavator, loader dozer, crane, etc., use the ascending and descending of the jib to perform operation, however, in existing lifting systems for the jib, the weight of the jib is always so great that, when the jib ascends, it's necessary for the power system of the operating machine to provide enormous force with high energy consumption, and the speed for elevating the jib is relatively low; and when the jib descends, the gravitational potential energy of the jib is often wasted and can't be effectively utilized. Although some systems capable of recycling the gravitational potential energy when jib descends have been developed, these systems are complicated in their configuration, inconvenient in operation, and cannot effectively release the recovered energy to lift the jib quickly.